Hydraulic Workover Techniques: Their Versatility and Applications

Abstract

SPE Member Abstract The increased impetus on economic efficiency and safety in oil and gas service operations has challenged the industry to seek newer and better strategies that are able to comply with current operational needs. In response to these challenges, state-of-the-art hydraulic workover (HWO) equipment and systems, which can provide alternative methods to traditional drilling and workover operations and can comply with economic and safety constraints, have now been developed. These new systems not only enhance problem-solving options but also increase protection of service personnel and the environment. This paper will discuss the broader range of applications that has emerged as a result of improvements in HWO technology, the history of these systems, new HWO capabilities, components of the new systems, and safety enhancements recently introduced to the industry. Case histories will provide supporting data. Introduction and History While performing drilling or workover operations, operators have routinely encountered situations that exceed the capabilities of conventional derrick-based equipment. The development of new HWO well servicing techniques can now address these needs. New, more compact equipment can perform not only routine drilling and workover rig functions but also operations under pressure that are beyond the scope of derrick-based equipment. In many situations, hydraulic workover procedures involve moving pipe under pressure rather than when the well is "dead." To force, or "snub," a pipe into a pressurized well bore, a seal must first be established on the internal diameter of the pipe to prevent the hydrocarbons from blowing up through the pipe during the operation. Often, this internal seal consists of a check valve (or a pair of check valves) to be placed as part of the bottomhole assembly (Figure 1). These check valves allow fluids to be pumped down the string of pipe but check any flow in the upward direction. At other times, such as when installing a velocity string (also called a siphon string), the internal seal is provided by a wireline removable plug or other subsurface flow control device (Figure 2). A second requirement in snubbing operations is that a seal be established between the wellbore and the outside diameter of the pipe that is being forced into the wellbore. This seal prevents hydrocarbons from blowing up through the annular space. The seal is provided by a normal oilfield blowout preventer (BOP) with modified sealing surface materials (Figure 3). P. 115^

An Emergency Escape System for an Elevated Workplace

“…Since it is much smaller than a derrickbased unit and mounts directly onto the wellhead, a large load-bearing surface such as required for a derrick-based rig is not needed (Figure 1). 3,4 The unit uses large, pressure-sealing blowout preventer (BOP) devices, a diesel-powered hydraulic system, a large hydraulic jack, and pipe-gripping devices (slips) to force the pipe downward or lift it upward. Check valves are used in the pipe string to prevent well fluids and gases from escaping through the pipe.…”